THE ANATOMY OF THE STEM OF THE PAPAVERACTLE. 597 



appear as age progresses. The distribution of the elements could not therefore be 

 determined with certainty. 



Corydalis racemosa, Pers. — The epidermal and subepidermal cells in this form 

 have curiously folded walls (fig. 26). Though furrowed like Adlumia, subepidermal 

 collenchyma is absent. The endodermis is not distinguishable, and the pericycle 

 is only slightly sclerotic and varies in thickness. Cells with folded walls similar to 

 those found in the epidermis and subepidermis also appear in the conjunctive 

 parenchyma surrounding the vascular bundles or scattered among other cells on 

 the inner side of the vascular bundles (fig. 27). Similar cells with folded walls occur 

 in other species of Corydalis and also in species of Argemone, Dicentra, and 

 Eschscholzia. Latex occurs in the subepidermal layer, in the conjunctive parenchyma 

 of the vascular bundles, and also but to a less extent in the xylem and phloem. 

 Some of the medullary ray- and medullary cells also contain latex, but in trifling 

 amount, and in all cases it tends to disappear in the adult. 



Corydalis glauca, Pursh., agrees in its anatomy with C. racemosa in all 

 essentials, as does also C. capnoides, Wahl. 



As has been already pointed out under Papaver Rhoeas, the anatomy of the 

 stem base may differ considerably from that of the aerial portion, and a few notes 

 may be added as to the peculiarities of that region in other species of Papaver and 

 in the genera just discussed. The only point worthy of note in the stem bases of 

 P. dubium and P. somniferum is the feebleness of the lignification, while in 

 P. pilosum the secondary wood even consists of only a few xylem vessels scattered 

 among thin-walled, slightly prosenchymatous cells. 



In P. orientate Leger states that the vascular bundles remain isolated even at 

 the base of the stem, and arrange themselves in one or two cycles. This is not the 

 case, however, as may be seen in fig. 28, where the bundles are not isolated though 

 their individuality may still be made out by their protoxylems. Leger also 

 emphasises the permanence of hard bast in the basal region, in contrast with the 

 condition obtaining in preceding species. It is true that the bast fibres do persist 

 for some time, but eventually they disappear entirely. One point of interest not 

 noticed by Leger is the occurrence of a secondary zone of cambial activity inside 

 the vascular ring, i.e. in the medulla, which produces xylem outwards and phloem 

 inwards (figs. 29, 30). The two xylem zones, the outer formed by the normal the 

 inner by the medullary cambium, are separated by a layer of cells identical with those 

 of the medulla, though in some places the two xylems are practically confluent. 



Save for variations in the degree of sclerosis in the medulla and medullary 

 rays and in the amount of secondary xylem formed, the stem bases of the remain- 

 ing species of Papaver examined do not call for any special description. The 

 secondary phloem in the stem base of Meconopsis cambrica exhibits abundant latex, 

 tubes arranged in concentric circles. No special features call for mention in the 

 stem bases of Argemone mexicana, A. hispida, A. ochroleuca, Chelidonium majus, 

 TRANS. ROY. SOC. EDIN., VOL. LI, PART III (NO. 18). 87 



